Lift - Newton/Bernoulli ratio...

Dudley Henriques writes:

Actually, if I'm reading you right, I would rephrase this just a bit,
as it feeds into the problems we as instructors have in "re-
explaining" lift to students.
STRESSING either Newton or Bernoulli in the lift explanation causes
more than a modicum of confusion UNLESS it's done by including BOTH
theories in the explanation. You've done that actually. I would just
enhance things a bit more :-)

Agreed.

The problem is that all these effects interact, and explaining lift is often a
matter of preferred viewpoint, as you imply.

But it is true that lift always involves the acceleration of an air mass,
which is a matter of Newton's third law. How this acceleration is accomplished
is irrelevant, provided that it occurs. Bernoulli's effect and many other
effects help to explain why air flowing over an airfoil with a positive angle
of attack is accelerated at right angles to the direction of flow, but these
effects don't produce the lift directly, it's the acceleration that produces
the lift.

If you build something that accelerates an air mass in the same way without
any connection to Bernoulli et al., it will still fly. On the other hand, if
you build something that demonstrates Bernoulli's effect but does not
accelerate air perpendicular to its flow, no lift results.

When I dealt with the lift issue with instructors in seminar, my
personal approach was to favor the Newtonian explanation as in my
opinion student pilots can grasp Newton a lot easier than Bernoulli,
but I've ALWAYS made it habit NEVER to leave Bernoulli out in the
cold.

Lift is produced by diverting the air flow, thanks to Newton. The diversion in
an airfoil is in part produced thanks to Bernoulli.